What's more is that most people in the mainly Russian-speaking Crimean peninsula, an autonomous region that is home to the Kremlin's Black Sea fleet, are just fine with the situation. In fact, their new prime minister invited Moscow's intervention, ostensibly to "guarantee peace" amid the political chaos in Kiev.

NPR's Peter Kenyon, reporting from the Crimean city of Simferopol, says pro-Russian Crimeans make up a majority in the region and most "seem untroubled by the effective military occupation of their territory."

"For many, it's reassuring to hear that Russian forces now control most strategic assets in Crimea," Kenyon reports on Weekend Edition Sunday.

After months of anti-government protests, Ukraine's pro-Russia President Viktor Yanukovych was ousted last week and replaced by a more Western-leaning interim government. The move was immediately condemned by Russian President Vladimir Putin, who described it as a "coup." Thursday's military intervention reflects a fear that Ukraine, long closely tied to Moscow, will "somehow spin out of the orbit of Russia," Steven Lee Myers, Moscow bureau chief for The New York Times, tells WESUN host Jacki Lyden.

On Sunday, Ukrainian leaders made allusions to a state of war with Russia, with Prime Minister Arseniy Yatsenyuk calling on Putin to pull back his troops and warning that the two sides were "on the brink of disaster."

But Olga Oliker, associate director of Rand Corp.'s International Security and Defense Policy Center, speaking with CNBC on Friday, said that "if Crimea decides it wants to be part of Russia, all Ukraine can hope to do is get the EU and U.S. to intervene on its behalf." She says that kind of military help is highly unlikely.

Michael McFaul, who was the U.S. ambassador to Russia until just last week, tell WESUN: "I think the [U.S.] response will be political."

As for Ukraine, Myers tells NPR that its forces would be at a distinct disadvantage a conflict with Russia.

"They haven't been tested like Russian forces have been in various conflicts from Chechnya to Georgia in 2008," he says.

"The Russian military is obviously much larger, better equipped, had some moves toward modernization, especially under Putin, with new armaments and so forth," Myers says. "So, I think it would not necessarily be an even fight. That said, [Ukraine's is] not a small army and they do have capabilities. The question is would they be able to hold together and put up some sort of resistance, if it comes to that."

Already, however, there the occupation of Crimea might be irreversible.

On Sunday Ukraine's navy chief, Rear Admiral Denis Berezovsky, appointed only Saturday, "defected" a day later. Berezovsky appeared before cameras in the Crimean port of Sevastopol alongside the region's newly installed pro-Russian Prime Minister Sergei Aksyonov, who said he'd ordered all Ukrainian naval forces on the peninsula to disregard any orders coming from Kiev. Later the deputy head of Ukraine's Security Council said Berezovsky had been fired.

Earlier Reuters quoted Ukrainian officials as saying the country's 10 warships were in Sevastopol and remained loyal to the government, but that its coast guard vessels had steamed for safer ports on the Black Sea, in Odessa and Mariupol.

"Curiously, [Sunday], you see a sort of pause," he tells NPR. "The Kremlin says that Putin hasn't yet made a decision about whether to use or deploy force [in the rest of Ukraine] and we're waiting to see what happens next."

For resident Galena Moisyeva, strolling the streets of a largely quiet downtown Simferopol, if Russian control of Crimea means "what comes next" is parting ways with the rest of Ukraine, she's OK with that.

"You talk about troops, but you can see we just came from the theater, we don't see any troops," she told NPR's Kenyon. "In Kiev, the authorities are illegal, we don't like this. We ask for Crimea to be separated from Ukraine, but we don't ask to join Russia.

"Putin gives us guarantees that what happened there in Kiev won't happen here."